1. Field of the Invention
This invention relates to general utility and specialized purpose blade manufacturing techniques and products produced thereby, and in particular, to a method of using wire electric discharge machining to machine the cutting portion of bone saw blades from metal blanks mounted in a jig.
2. Description of the Prior Art
Bone saw blades for use in oscillating cutting surgical instruments have traditionally been machined from metal by grinding, filing, and stamping processes. These processes limit the height and profile of the teeth of the resultant bone saw blades and can create unwanted burrs on the blades. As an example, a typical bone saw blade manufactured by a grinding process might have a tooth angle of 64 degrees, a tooth ridge angle of 90 degrees, a cutting surface angle of 60 degrees, a tooth depth of 0.073 inches, a distance between teeth of 0.0833 inches, and a radius of curvature of 3.5 inches. As will be apparent in the following description, the blades of the invention have teeth of greater height with an improved cutting profile.
Another method of machining metal is electric discharge machining (EDM). Most EDM processes operate under the same principles. A positively charged electrode and a negatively charged workpiece are separated by a dielectric medium or fluid. Direct current causes a spark discharge, or arc, between the workpiece and the electrode. The sparks remove material from the workpiece through melting or vaporization and the dielectric medium cools the workpiece and flushes away removed material.
There are basically two types of EDM, traditional EDM and wire EDM. Under traditional EDM, a flowing dielectric fluid in the spark gap provides a pathway for the spark and flushes away removed material. Traditional EDM is primarily used to produce die surfaces for small precision parts. Wire EMD works under the same principle but uses a wire electrode which cuts through the workpiece like a bandsaw when direct current passes through the wire electrode. Wire EDM, under numeric or computer control, can cut two dimensional openings to a precision of 0.0005 inches with roughnesses as low as 10 .mu.m. Electrodes for traditional EDM are often made of copper, brass, aluminum, or steel. The materials for wire electrodes include copper, brass, zinc, boron, and composites containing steel. Wire EDM is also referred to as traveling wire EDM.
EDM processes have been known for many years and have been utilized in a variety of manufacturing processes. Despite the existence of EDM processes and their use in various industries, such techniques have not been utilized in the manufacture of bone saw blades with cross-cut style teeth, to the best of applicant's knowledge.
An object of the present invention is to provide an improved process by which cutting blades can be manufactured, particularly surgical cutting blades.
Another object of the invention is to provide an improved bone saw cutting blade which is sharper and easier to use, which cuts more efficiently, which generates less heat during manufacturing, which requires less deburring, and which reduces the chances of thermal necrosis while in use.
Another object of the invention is to provide an improved bone saw cutting blade which is relatively simple in design and economical to manufacture.
Another object of the invention is to provide a process for manufacturing surgical blades which allows the blade teeth to have increased height and depth and more pronounced profiles as compared to the prior art.
Another object of the invention is to utilize an EDM machining process to manufacture the cutting blades of the invention, which process is readily adapted to computer control to thereby facilitate frequent or necessary changes in the geometry of the blade teeth.
Another object of the invention is to provide cutting teeth with profiles that would be extremely difficult, if not impossible, to machine with conventional methods.